freebsd-update: Error for -b basedir without UNAME_r set

[emaste]

Summary

freebsd-update sets the currently running release from UNAME -r, which
can be overridden via the --currently-running commandline option (or by
setting UNAME_r in the environment).  This is not valid if -b is used to
specify a basedir other than /, so error out if -b is specified without
setting the currently running version.

PR:             283229

[des]

seems reasonable to me, but we should check with @cperciva

[jrtc27]

usr.sbin/freebsd-update/freebsd-update.sh

762

[emaste]

typo fix from @jrtc27

[cperciva]

You can use -b basedir just fine without setting --currently-running if it's the same version as the base system.

This seatbelt is probably useful but it's not strictly *necessary*.

[emaste]

To me it seems reasonable to require an explicitly specified --basedir. The PR that prompted this review at least had a fairly straightforward error, but I imagine that someone trying to update a 14.1-RELEASE basedir on a 14.2-RELEASE system would fail in even more surprising ways, as it wouldn't trigger the "can't update other than a release" error.

If you think this is a use case we need to accommodate I could make this a warning instead, e.g. WARNING: -b basedir set without --currently-running and perhaps also basedir must contain the same version as installed on the host. But I would rather have the user specify the version rather than supporting a case that may or may not work.

[emaste]

In D48016#1094886, @emaste wrote:

To me it seems reasonable to require an explicitly specified --basedir. The PR that prompted this review at least had a fairly straightforward error, but I imagine that someone trying to update a 14.1-RELEASE basedir on a 14.2-RELEASE system would fail in even more surprising ways, as it wouldn't trigger the "can't update other than a release" error.

If you think this is a use case we need to accommodate I could make this a warning instead, e.g. WARNING: -b basedir set without --currently-running and perhaps also basedir must contain the same version as installed on the host. But I would rather require that the user specify the version than supporting a case that may or may not work.

[jrtc27]

Is there a reason to not do the right thing automatically via ROOT=... freebsd-version?

[emaste]

Is there a reason to not do the right thing automatically via ROOT=... freebsd-version?

Mmm, we do that for -j already, that sounds like a good idea. I'd probably emit a notice about the detected version to make it clear.

[emaste]

ROOT=... freebsd-version?

It doesn't look like that would work -- we'd have to execute $BASEDIR/freebsd-version as USERLAND_VERSION is baked into the script. I'll take a look at that, but as a subsequent commit.

[cperciva]

I'm not convinced that it's strictly necessary, but I guess that's the nature of seat belts. Certainly seems harmless enough.